/*
 * Copyright (C) 2012 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.util.concurrent;

import static org.mockito.Answers.CALLS_REAL_METHODS;
import static org.mockito.Mockito.doReturn;
import static org.mockito.Mockito.mock;

import com.google.common.base.Function;
import com.google.common.collect.ForwardingObject;
import com.google.common.collect.Iterables;
import com.google.common.testing.ForwardingWrapperTester;

import java.lang.reflect.Method;
import java.util.Arrays;

/**
 * Tester for typical subclass of {@link ForwardingObject} by using EasyMock partial mocks.
 *
 * @author Ben Yu
 */
final class ForwardingObjectTester
{

    private static final Method DELEGATE_METHOD;

    static
    {
        try
        {
            DELEGATE_METHOD = ForwardingObject.class.getDeclaredMethod("delegate");
            DELEGATE_METHOD.setAccessible(true);
        }
        catch (SecurityException e)
        {
            throw new RuntimeException(e);
        }
        catch (NoSuchMethodException e)
        {
            throw new AssertionError(e);
        }
    }

    /**
     * Ensures that all interface methods of {@code forwarderClass} are forwarded to the {@link
     * ForwardingObject#delegate}. {@code forwarderClass} is assumed to only implement one interface.
     */
    static <T extends ForwardingObject> void testForwardingObject(final Class<T> forwarderClass)
    {
        @SuppressWarnings("unchecked") // super interface type of T
        Class<? super T> interfaceType =
                (Class<? super T>) Iterables.getOnlyElement(Arrays.asList(forwarderClass.getInterfaces()));
        new ForwardingWrapperTester()
                .testForwarding(
                        interfaceType,
                        new Function<Object, T>()
                        {
                            @Override
                            public T apply(Object delegate)
                            {
                                T mock = mock(forwarderClass, CALLS_REAL_METHODS);
                                try
                                {
                                    T stubber = doReturn(delegate).when(mock);
                                    DELEGATE_METHOD.invoke(stubber);
                                }
                                catch (Exception e)
                                {
                                    throw new RuntimeException(e);
                                }
                                return mock;
                            }
                        });
    }
}
